Attenuation of P- and S-waves as a method of distinguishing gas and condensate from oil and water

Compressional- and shear-wave attenuation data were calculated from sonic waveforms in three wells. The results show that at similar porosities and at in-situ conditions, gas and condensate sandstone reservoirs exhibit higher P-wave attenuation (lower P-wave quality factor, Q p ) than either fully-water or partially «oil+water» saturated sandstones. However, S-wave attenuation and quality factor Q S do not show such a strong dependence on pore fluids. Furthermore, Q P /Q S <1 indicates presence of gas or condensate, while Q P /Q S - I indicates «full water» or «oil+water» saturation. These field data are consistent with laboratory data and theoretical predictions by various researchers. The crossovers of P-Swave attenuation and Q P -Q S quality factors proved useful for distinguishing gas and condensate from oil and water reservoirs. They may be used in conjunction with Vp/Vs and other logs as an aid in formation evaluation for the detection of gas, condensate, and oil. Several case studies in the literature report high P-wave energy absorption at seismic frequencies below gas and condensate pools. This suggests that it is not unreasonable to assume that this method could also be used in seismic exploration as an aid for distinguishing gas and condensate from oil and water formations

[1]  N. Dutta,et al.  On White's model of attenuation in rocks with partial gas saturation , 1979 .

[2]  M. B. Widess.  HOW THIN IS A THIN BED , 1973 .

[3]  G. McMechan,et al.  ANALYSIS OF ABSORPTION AND DISPERSION EFFECTS IN SYNTHETIC tau -p SEISMOGRAMS. , 1987 .

[4]  R. Kleinberg,et al.  Acoustic relaxation in sedimentary rocks; dependence on grain contacts and fluid saturation , 1986 .

[5]  Amos Nur,et al.  Wave attenuation in partially saturated rocks , 1979 .

[6]  M. Toksöz,et al.  Reply [to “Comment on ‘Determination of in situ attenuation from full waveform acoustic logs’ by C. H. Cheng, M. N. Toksöz, and M. E. Willis”] , 1984 .

[7]  B. Zinszner,et al.  Saturation Methods And Attenuation Versus Saturation Relationships In Fontainebleau Sandstone , 1984 .

[8]  M. Biot.  MECHANICS OF DEFORMATION AND ACOUSTIC PROPAGATION IN POROUS MEDIA , 1962 .

[9]  K. Winkler.  The effects of pore fluids and frictional sliding on seismic attenuation , 1979 .

[10]  William F. Murphy,et al.  Effects of partial water saturation on attenuation in Massilon sandstone and Vycor porous glass , 1982 .

[11]  V. V. Churlin,et al.  Application of Seismic Surveying to Recognition of Productive Part of Gas-Oil Strata , 1963 .

[12]  J. W. Spencer.  Bulk and shear attenuation in Berea Sandstone: The effects of pore fluids , 1979 .

[13]  T. Klimentos,et al.  Attenuation of Compressional Waves In Water-saturated Sandstones By Intra-pore Clay Minerals , 1988 .

[14]  A. L. Frisillo,et al.  Effect of partial gas/brine saturation on ultrasonic absorption in sandstone , 1980 .

[15]  J. H. Rosenbaum,et al.  Acoustic waves from an impulsive source in a fluid‐filled borehole , 1966 .

[16]  N. Dutta,et al.  Attenuation and dispersion of compressional waves in fluid-filled porous rocks with partial gas saturation (White model); Part I, Biot theory , 1979 .

[17]  Terry D. Jones,et al.  Pore fluids and frequency‐dependent wave propagation in rocks , 1986 .

[18]  Amos Nur,et al.  Seismic attenuation: Effects of pore fluids and frictional-sliding , 1982 .

[19]  M. Wyllie,et al.  Effects of Pressure and Fluid Saturation on the Attenuation of Elastic Waves in Sands , 1964 .

[20]  Amos Nur,et al.  Pore fluids and seismic attenuation in rocks , 1979 .

[21]  R. E. Sheriff,et al.  Application of Amplitude, Frequency, and Other Attributes to Stratigraphic and Hydrocarbon Determination: Section 2. Application of Seismic Reflection Configuration to Stratigraphic Interpretation , 1977 .

[22]  I. Palmer,et al.  Attenuation by squirt flow in undersaturated gas sands , 1980 .

[23]  Bernard Budiansky,et al.  Viscoelastic properties of fluid-saturated cracked solids , 1977 .

[24]  Nigel Allister Anstey,et al.  Seismic interpretation : the physical aspects : being a record of the short course 'The New Seismic Interpreter' presented under the auspices of International Human Resources Development Corporation , 1977 .

[25]  M. B. Dobrin.  Introduction to Geophysical Prospecting , 1976 .